A difficult obstacle associated with the exploration and production of oil and gas is management of significant ocean currents. These currents can produce vortex-induced vibration (VIV) and/or large deflections of tubulars associated with drilling and production. VIV can cause substantial fatigue damage to the tubular or cause suspension of drilling due to increased deflections. Both helical strakes and fairings can provide sufficient VIV suppression.
Fairings are a popular VIV suppression device. Fairings are placed around a tubular (on a collar that clamps to the tubular to restrain the fairing from sliding along the tubular's longitudinal axis more than desired) and are free to rotate (weathervane) with changes in current direction.
Present fairings utilize a design that is split in the tail (e.g., along the tail axis). During installation, the fairing is placed around the tubular and the tail sections are aligned and fastened at several locations to keep the fairing closed around the tubular. In some cases, there are several internal support blocks that also must be fastened to the tubular after the fairing is placed around the tubular. This design means that numerous fasteners must be installed to close the fairing around the tubular and have it sufficiently supported by the internal blocks. The result is that the installation can be quite time consuming. Since installation vessels have very high day rates, the cost of installing fairings can be substantial.
In addition, the internal support blocks are often cut from a sheet of material or injection molded and can therefore be slow to manufacture. In addition, they add a significant component to the overall fairing cost. Moreover, in order to function properly, it is important that the fairings be free to rotate with changes in current direction. Marine growth, however, can inhibit this rotation.